Blues 2, Penguins 1: Defenseman Kevin Shattenkirk scored at 10:52 of the third period to snap a tie and lift host St. Louis to its sixth win in seven games.
Ryan Reaves also tallied and Jaroslav Halak made 19 saves for the Blues, who improved to 2-0-0 on their five-game homestand and 7-1-2 in their last 10 overall contests.
Jussi Jokinen scored the lone goal for the Penguins, who have dropped two straight following a four-game winning streak. Marc-Andre Fleury stopped 30 shots as Pittsburgh produced fewer than four goals for the ninth time in 10 games.
A seemingly harmless shot proved to be the decisive one. Shattenkirk fired the puck toward the net from the right point, and the puck managed to sneak past Fleury and trickle over the goal line to give St. Louis a 2-1 edge.
After a scoreless first period, St. Louis took the lead 2:52 into the second as Reaves redirected Maxim Lapierre's feed past Fleury from the left hash marks. Pittsburgh pulled even during a power play at 8:06, when Jokinen accepted a pass from Evgeni Malkin and beat Halak from the doorstep.
GAME NOTEBOOK: Pittsburgh LW James Neal made a surprise return to the lineup and notched an assist. The 26-year-old had been sidelined since suffering an upper-body injury in the season opener. ... The Penguins also welcomed back RW Beau Bennett from a lower-body injury but were without D Paul Martin (undisclosed). ... St. Louis D Jordan Leopold did not play after being injured while blocking a shot in Thursday's win over Calgary.